Red Hat Bugzilla – Bug 562075
kernel: vfs: add MNT_NOFOLLOW flag to umount(2) [mrg-1]
Last modified: 2016-05-22 19:30:01 EDT
+++ This bug was initially created as a clone of Bug #562072 +++
Description of problem:
[RFC PATCH] vfs: add MNT_NOFOLLOW flag to umount(2)
From: Miklos Szeredi <email@example.com>
Add a new MNT_NOFOLLOW flag to umount(2). This is needed to prevent
symlink attacks in unprivileged unmounts (fuse, samba, ncpfs).
Additionally, return -EINVAL if an unknown flag is encountered. This
makes it possible for the caller to determine if a flag is supported
or not (at least on kernels with this patch).
Discussion is at:
Patch bz562075-vfs-add-MNT_NOFOLLOW-flag-to-umount.patch, backport of upstream commit db1f05bb85d7966b9176e293f3ceead1cb8b5d79, has been added to kernel -159 patch queue.
Technical note added. If any revisions are required, please edit the "Technical Notes" field
accordingly. All revisions will be proofread by the Engineering Content Services team.
Added the MNT_NOFOLLOW option to the umount(2) system call. This prevents umount(2) from following symlinks and avoids symlink attacks on unprivileged umounts on filesystems such as fuse, samba and ncpfs.
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.